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Unlocking the secrets of a killer

Unlocking the secrets of a killer

Scientists are making significant progress to improve the testing and treatment of the killer illness salmonella.

Achieving success is vital because every year almost one in ten people fall ill to food-borne illnesses, with many of them dying, according to the World Health Organisation (WHO).

According to the WHO, diarrhoeal diseases are the most common of the illnesses resulting from unsafe food with 550 million people falling ill each year, including 220 million children under the age of five years, and salmonella is the cause in a quarter of the cases.

Salmonella is a ubiquitous and hardy bacteria that can survive several weeks in a dry environment and several months in water, making it particularly resilient.

Now, a new test developed by American researchers has been developed which allows accurate and rapid testing for the bacteria.

The breakthrough could have wide-raging applications because salmonella can infect animals as well as people, with commonly reported cases of people falling sick after handling pets and livestock.

The new method, first developed for automated food safety testing then adapted by Cornell University scientists for a wider range of sample types, can detect the bacteria from samples including swabs, feces, milk and blood.

Tests to confirm the presence of the bacteria used to take days but, thanks to the new technique, they can take 24 hours, with a hundredfold improvement in detection for at least one type of Salmonella, called Salmonella Dublin, which is difficult to grow in culture, making diagnosis difficult.

Salmonella Dublin is ‘host-adapted’ in cattle, meaning that infected animals can become permanent or long-term carriers, putting herds, especially susceptible calves, at risk.

The strain can infect people who may be exposed by contact with infected animals, by drinking raw milk, or by consuming other contaminated food products. It has higher hospitalisation and fatality rates than other Salmonella types, causing infection of body tissues, similar to typhoid.

Belinda Thompson, assistant clinical professor at Cornell’s Animal Health Diagnostic Center and a senior author of the paper outlining the research, said: “Because we have this 24-hour turnaround time with the new test, there are veterinary hospitals and clinics that can test and get results rapidly and make sure they are not exposing other animals to Salmonella. Fast clinical diagnoses also allow veterinarians to quickly quarantine an infected animal.”

Work on the test was funded and developed in collaboration with the Food and Drug Administration (FDA) Veterinary Laboratory Investigation and Response Network. Cornell works closely with FDA scientists to evaluate and perform new methods that the government agency can share with other veterinary labs.

Research deepens understanding of salmonella

Understanding the way salmonella works is crucial for vets and doctors alike and now techniques created by scientists at the Norwich Research Park in the UK are helping to uncover what makes certain strains of bacteria more dangerous than others.

There are many different types of salmonella bacteria, most of which have adapted to live in the guts of different animals, including humans, other mammals and birds, and some of these strains have further evolved extra abilities to evade their hosts’ immune defences. These types of salmonella are of most concern as they cause the most severe disease, including typhoid.

To understand what makes certain strains so invasive, researchers have been looking at the genetic differences between these and less invasive strains.

Dr Tamás Korcsmáros, a systems biologist from the Quadram Institute (QI) and the Earlham Institute, has led the development of SalmoNet alongside a research group at QI with expertise in salmonella infection, led by Dr Rob Kingsley.

As part of the work, Professor Jozsef Baranyi used network biology and bioinformatic techniques to collate molecular interactions within salmonella, and to link information on how genes and metabolic pathways are regulated and how proteins interact with each other.

The results of the work are being used to find out how bacteria adapt to their environment and how the disease evolves, the first time that this type of approach has been used to investigate salmonella.

Team members hope that the work may help identify potential drug targets, and help in the development of new therapies against systemic salmonella infections.

The research was supported by BBSRC.

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